Marc Perron

Three-dimensional gait analysis in women with a total hip arthroplasty

OBJECTIVES The purposes of this study were: (1) to identify the primary (hip) and secondary (neighboring joints) impairments during gait in subjects with a total hip arthroplasty total hip arthroplasty, (2) to determine which impairments persist when controlling for gait speed and (3) to study the relationships between primary and secondary impairments in order to describe the locomotor strategies used by these patients.DESIGN. This cross-sectional study compared the gait patterns of women with a total hip arthroplasty to those of healthy women.BACKGROUND. Several studies have reported residual hip impairments in the sagittal plane during gait after a total hip arthroplasty. There is, however, a substantial lack of knowledge in regard to the changes at the neighboring joints and in the other planes of movement.METHODS. Subjects have been examined during a gait laboratory testing session including the simultaneous recording of three-dimensional kinematics and ground reaction forces on one side, and bilateral activation of six lower limb muscles.RESULTS. A significant decrease of 20% in the hip extensor moment of force during the early stance phase was correlated (R(2)=43%) with a significant decrease of 14% in gait speed. Moreover, a significant decrease of 59% in the range of hip extension at the end of the stance phase was observed together with secondary impairments such as a significant increase in the anterior pelvic rotation, in knee flexion and in ankle dorsiflexion. Lastly, a significant increase in ipsilateral bending of the trunk during the single limb support on the operated limb was concomitant with a significant decrease in the hip abductor moment of force.CONCLUSIONS. The decrease in gait speed and the persistence of abnormal gait patterns one year after the total hip arthroplasty were associated respectively with a decrease in the hip extensor moment of force and with a decrease in the range of hip extension (sagittal plane) or in the hip abductor moment of force (frontal plane). RelevanceThe data provided in this paper may serve as guidelines to establish rehabilitation programs designed to restore optimal locomotor function.

Acetic acid lontophoresis and ultrasound for the treatment of calcifying tendinitis of the shoulder: A randomized control trial

Abstract Objective: To assess the effects of acetic acid iontophoresis (AAI) and ultrasound on calcifying tendinitis of the shoulder, and to determine the relation between changes in the radiological measures of calcium deposit (CD) and shoulder function. Design: Randomized control trial. Setting: General community, private practice. Patients: Twenty-two adults (7 men, 15 women) with a calcifying tendinitis of the shoulder, without associated conditions, stratified according to the type of lesions (X-ray: type I, fleecy appearance; type II, homogeneous), were randomly allocated to an experimental (EXP, n = 11) or to a control (CTL, n = 10) group. Interventions: CTL group, no treatment; EXP group, nine treatments including AAI (5% acetic acid solution via the negative electrode, 5mA galvanic current, 20 minutes) followed by continuous ultrasound (0.8w/cm 2 , 1MHz, 5 minutes). Main Outcome Measures: Area and density of the CD, passive shoulder abduction (range of motion [Rom]), pain intensity. Results: Significant reduction in the area and density of CD (ANCOVA, p = .01 and .03) over time in the EXP and CTL groups, but no significant difference between groups for any of the variables measured. The decrease in the area of CD in type I lesions ( n = 5) was larger (Mann-Whitney U test, p n = 16) lesions. The relation was stronger ( r s = .90) between changes in area and density of CD than between ROM and pain ( r s = .67). Correlations were weak ( r s = .21 to .41) between radiological and functional changes. Conclusion: The reduction in CD area and density likely results from a natural process rather than treatment (AAI and ultrasound); type I lesions (resorptive phase) are more likely to display resorption of the CD than type II lesions (formative phase). Reduction of the CD area does not necessary result in a functional improvement.

Isometric muscle strength in youth assessed by hand-held dynamometry: a feasibility, reliability, and validity study.

Purpose: To determine, with respect to measurement of maximal isometric torque (MIT) using a specific hand-held dynamometer (HHD) protocol, (1) protocol feasibility over a wide age range, (2) intra- and interrater reliability, (3) standard error of measurement, and (4) concurrent validity. Methods: The MIT of selected upper and lower limb muscle groups was assessed (n = 74; age = 4-17.5 years) using a standardized, HHD protocol. Testing was repeated in 20 adolescents (n = 10 for each muscle group), who were also assessed with a Cybex dynamometer. Results: The protocol was feasible for all participants. Mean intra- and interrater reliability [intraclass correlation coefficient (ICC)] varied from 0.75 to 0.98, except for ankle dorsiflexor interrater reliability (mean ICC = 0.67). The standard error of measurement varied from 0.5 to 4.9 Nm and was highest for hip extensors. Mean concurrent validity (ICC) varied from 0.78 to 0.93, except for ankle plantar flexors (mean ICC = 0.48). Conclusions: Our HHD protocol was feasible over a wide age range and most MIT values were valid and reliable.

The ability of the Biodex Stability System to distinguish level of function in subjects with a second-degree ankle sprain:

Objective: To assess the capacity of the Biodex Stability System using a one-leg stance protocol to differentiate between injured and non-injured limbs and between level of disabilities. Design: Cross-sectional study. Setting: Military and civilian clinic. Subjects: Thirty-four individuals with a second-degree lateral ankle sprain and 36 healthy subjects. Methods and measures: Subjects were tested on the Stability System 30 days after injury using a one-leg stance protocol in the dynamic limit-of-stability mode. All subjects also filled out a disability questionnaire (Lower Extremity Functional Scale). The groups were compared based on the overall dynamic limit-of-stability score and its relationship with the score on the disability questionnaire was also examined. Results: The overall dynamic limit-of-stability scores (subjects with a lateral ankle sprain: 13.0% (5.5)-26.0% (9.2); healthy subjects: 16.9% (7.9)-27.9% (9.6)) clustered in the lower end of the theoretical range of 0–100%. Statistically significant differences in the overall dynamic limit-of-stability scores were found between the injured and non-injured limbs but group differences were small and clinically not relevant. No significant relationships were found between the overall dynamic limit-of-stability scores and the Lower Extremity Functional Scale scores (58.2 (11.8)) of the subjects with a lateral ankle sprain. Conclusions: The one-leg stance protocol carried out in the dynamic limit-of-stability mode is very challenging and offers a very limited capacity to differentiate between injured and non-injured limbs. The main outcome of the Stability System does not appear to be a good indicator of the functional capacity of people with a lateral ankle sprain.

Assessing advanced locomotor recovery after total hip arthroplasty with the timed stair test

Objective: To assess advanced locomotor performance with the timed stair test (TST) and to determine if the level of performance of a group of women one year after hip replacement changed with the functional demands of the tasks. Design: Comparison of the performance of two groups of women. Setting: General community. Participants: A convenient sample including 18 women who had had a total hip replacement 11 months earlier (patients) and 15 healthy age-matched women (comparison group). Main outcome measures: Three tests were administered: the 10-m walk test, the unloaded TST and the loaded TST (10 kg). The duration of each test was recorded and transformed into speed and the level of performance was assessed by calculating percentage deficit using corresponding values from the comparison group. The TST is made of four subtasks: (1) standing up and walking, (2) ascending stairs, (3) turning and descending stairs, (4) walking back, turning and sitting down. Results: Significant differences in performance were found for all three tests with the patients showing a slower performance. The percentage deficits increased significantly from the less difficult (walking: 18%) to the more difficult conditions (unloaded TST: 23% and loaded TST: 28%), with the greatest deficits found during stair descent. Strong correlations were also found between walking deficits and TST deficits (loaded: r = 0.82; unloaded: r = 0.88). Conclusions: By combining mobility, walking and stair activities, the TST can be used to assess various components of advanced locomotor performance. The progressive level of difficulty of the TST subtasks as well as the addition of a load make it useful to detect subtle locomotor disabilities.

Full Load Range Neural Network Efficiency Optimization of an Induction Motor with Vector Control using Discontinuous PWM

Model-based efficiency controllers of induction motors (IM) are known to considerably reduce power losses for loads under 0.50 p.u. by correctly setting the flux under rated value. However, for loads higher than 0.5 p.u., their performance is approximately the same as rated flux vector controllers. It has been recently shown that switching losses and harmonic losses reduction for voltage source inverter (VSI) fed IM can be done by using a discontinuous PWM strategy (DPWM). Hence, this paper proposes a full load range efficiency optimization controller by using an artificial neural network (ANN)-based flux optimizer and a DPWM strategy for both low and high loads. The controller is validated by using a simulation model and comparing its performance with a conventional rated flux controller with space vector PWM (SVPWM). Full load range optimization is achieved with a reduction of fundamental losses of 27% at light load and a 47% reduction of switching and time harmonics losses at high load

Alteration in global motor strategy following lateral ankle sprain

BackgroundLateral ankle sprain (LAS) has often been considered an injury leading to localized joint impairments affecting the musculoskeletal system. Persistent chronic ankle instability and bilateral alterations in motor control after a first ankle sprain episode suggest that the origin of relapses might be a maladaptive reorganization of central motor commands. The objectives of this study were (1) to compare the quality of motor control through motor strategy variables of two groups (with and without LAS) from a military population (n = 10/group), (2) to evaluate the contribution of the lower limbs and the trunk to global body strategy and (3) to identify which global variable best estimates performance on the Star Excursion Balance Test (SEBT) for each group, reaching direction, and lower limb.MethodsPersonal and clinical characteristics of the participants of both groups were collected. Their functional ability was measured using questionnaires and they performed a series of functional tests including the SEBT. During this test, the maximal reach distance (MRD) and biomechanical data were collected to characterize whole body and segmental strategies using a 3D motion capture system.ResultsAt maximal lower limb reach, participants with LAS had a smaller variation in their vertical velocity in lowering-straightening and lowered the body centre of mass less for all injured limb conditions and some conditions with the uninjured lower limb. The global body centre of mass variables were significantly correlated to SEBT performance (MRD).ConclusionModifications in global motor strategies were found in participants with LAS as well as a decreased performance on the SEBT for the injured and uninjured lower limbs. These results support the hypothesis that following LAS, there may be a maladaptive reorganization of the central motor commands. Level of evidence: 3b.

Persistence of long term isokinetic strength deficits in subjects with lateral ankle sprain as measured with a protocol including maximal preloading

BACKGROUND The assessment of muscle function is a cornerstone in the management of subjects who have sustained a lateral ankle sprain. The ankle range of motion being relatively small, the use of preloading allows to measure maximal strength throughout the whole amplitude and therefore to better characterize ankle muscles weaknesses. This study aimed to assess muscle strength of the injured and uninjured ankles in subjects with a lateral ankle sprain, to document the timeline of strength recovery, and to determine the influence of sprain grade on strength loss. METHODS Maximal torque of the periarticular muscles of the ankle in a concentric mode using a protocol with maximal preloading was tested in 32 male soldiers at 8 weeks and 6 months post-injury. FINDINGS The evertor muscles of the injured ankles were weaker than the uninjured ones at 8 weeks and 6 months post-injury (P<0.0001, effect size=0.31-0.42). Muscle weaknesses also persisted in the plantarflexors of the injured ankles at 8 weeks (P=0.0014, effect size=0.52-0.58) while at 6 months, only the subjects with a grade II sprain displayed such weaknesses (P<0.0001, effect size 0.27-0.31). The strength of the invertor and dorsiflexor muscles did not differ between sides. INTERPRETATION The use of an isokinetic protocol with preloading demonstrates significant but small strength deficits in the evertor and plantarflexor muscles. These impairments may contribute to the high incidence of recurrence of lateral ankle sprain in very active individuals.